-er b-u bbb bbc bbd bbe bbo bbr bbu bcb bcc bcd bce bco bcr bcu bdb bdc bdd bde bdo bdr bdu be- beb bec bed bee beo ber beu bob boc bod boe boo bor bou brb brd bre bro brr bru bub buc bud bue buo bur buu c-- cbb cbc cbd cbe cbo cbr cbu ccb ccc ccd cce cco ccr ccu cdb cdc cdd cde cdo cdr cdu ce- ceb cec ced cee ceo cer ceu co- cob coc cod coe coo cor cou crb crc crd cre cro crr cru cub cuc cud cue cuo cur cuu dbb dbc dbd dbe dbo dbr dbu dcb dcc dcd dce dco dcr dcu ddb ddc ddd dde ddo ddr ddu de- deb dec ded dee deo der deu dob doc dod doe doo dor dou drb drc drd dre dro drr dru dub duc dud due duo dur ebb ebc ebd ebe ebo ebr ebu ec- ecb ecc ecd ece eco ecr ecu ed- edb edc edd ede edo edr edu eeb eec eed eee eeo eer eo- eob eoc eod eoe eoo eor eou erb erc erd ere ero err eru eu- eub euc eud eue eur ob- obb obc obd obe obo obr obu oc- ocb occ ocd oco ocr ocu odb odc odd ode odo odr odu oeb oec oed oee oeo oer oo- oob ooc ood ooo oor or- orb orc ord ore oro orr oru ou- ouc oud oue ouo our rbb rbc rbd rbe rbo rbr rbu rcb rcc rcd rce rco rcr rcu rdb rdc rdd rde rdo rdr rdu re- reb rec red ree reo rer reu rob roc rod roe roo ror rou rrb rrc rrd rrr rru rub ruc rud rue ruo rur ruu ubb ubc ube ubo ubr ubu ucb ucc ucd uce uco ucr ucu udb udc udd ude udo udr udu ueb uec ued uee uer uob uoc uod uoe uoo uor ur- urb urc urd ure uro urr uru uuc uue uur uuu